Petroleum streams that contain metals are typically problematic in refineries as streams because the metallic components contained therein have a negative impact on certain refinery operations. Thus, demetallation has been referred to as critical to help conversion of crude fractions (see e.g., Branthaver, Western Research Institute in Ch. 12, "Influence of Metal Complexes in Fossil Fuels on Industrial Operations", Am. Chem. Soc. (1987)). Such metals, for example, act as poisons for hydroprocessing and fluid catalytic cracking catalysts, thereby, shortening the run length of such processes, increasing waste gas make and decreasing the value of coke product from coker operations.
The presence of such metals prevents more advantageous use of the petroleum streams by rendering especially the heaviest oil fractions (in which these metal containing structures most typically occur) less profitable to upgrade, and when these resources are used make catalyst replacement/disposal expensive. Current refinery technologies typically address the problem by using metal containing feedstreams as a less preferred option, and by tolerating catalyst deactivation when there are not other feedstream alternatives available.
Electrochemical processes have been used for removal of water soluble metals from aqueous streams, see, e.g., U.S. Pat. No. 3,457,152. Additionally, U.S. Pat. No. 5,529,684 discloses the electrochemical treatment of refinery streams, which is carried out at specific cathodic potentials. Disclosed in the '684 patent as suitable electrodes are high hydrogen overpotential electrodes such as lead and zinc. There is a continuing need for cost effective methods for removal of metals from refinery feed streams. Applicant's invention addresses this need.